Evidence for an adsorbate-dependent mechanism for surface resistivity: formic acid, oxygen and CO on Cu(100)

When epitaxial Cu(100) films are exposed to formic acid, oxygen or CO gas a t low temperature, both the de electrical resistance and the infrared refle ctance of the film change. The ratio of the resistance change to the reflec tance change, however, is approximately twice as large for formic acid and CO as for oxygen, on identically prepared samples. This difference in slope is inconsistent with models in which the increase in film resistance arise s solely from scattering of conduction electrons by the adsorbates. Changes in conduction electron density may also be important for some systems, esp ecially when the chemisorption bond involves large charge transfer. (C) 200 0 Elsevier Science B.V. All rights reserved.